This invention relates to a sheet feed shaft used for a paper feed in a printing machine, a printer for an office machine and the like, and for a sheet feed such as a film in an overhead projector or the like.
A feed roller made of rubber has been widely used for a paper feed in a printer for an office machine. This tends to cause an unevenness in hardness of rubber, roundness, and concentricity with a shaft. Accordingly, in the case where multicolor printing is carried out by repeating the paper feed as in a color printing, a color deviation sometimes occurs due to the feed speed of paper and the deformation, and there occurs an inconvenience of unavoidably involving a change in quality and deformation caused by the wear of the feed roller.
On the other hand, there is disclosed, for example, in Japanese Patent Laid-Open No. Hei 7 (1995)-267396, a sheet feed shaft in which a metallic roller as a feed roller is integrally provided on a metallic shaft, a nickel plated layer is applied thereto, and after that, a sand blast processing is applied to the nickel plated layer of the metallic roller to make the surface a roughened surface.
According to the aforementioned publication, the roundness of the metallic roller can be secured and there occurs no wear or deformation. This can be therefore used as a multicolor roller.
However, in the conventional sheet feed shaft as described, since a number of hard small projections made of metal are formed on the surface of the feed roller, paper or sheets in contact therewith can be fed with high frictional resistance and in addition, the feeding can be secured for a relatively long period. However, since the small projections are relatively fine, there poses a problem in that dust stays between the small projections, the wear gradually progresses due to the feed operation so that the surface of the roller is gradually changed into a smooth surface, resulting in unusable.
Particularly, in the case where a sheet to be fed is a relatively hard film used in an overhead projector, there poses a problem in that the wear of the roller surface is particularly remarkable and cannot be fit for use for a long period of time, as a result of which the film cannot be arranged in an accurate position (on a light illuminating surface) so that a projected image is inclined.
There is a further problem in that the necessity to form a nickel plated layer or to apply a surface roughening by sand blast in order to form small projections on the metallic roller increases the number of processes and increases the cost of products accordingly.
This invention is to solve the problems as noted above. An object of this invention is to provide a sheet feed shaft, which can, merely by plastic processing with respect to the peripheral surface of a metallic rod, feed paper or a sheet such as a hard film in an intended direction while maintaining an accurate position thereof.
It is a further object of this invention to provide an apparatus for manufacturing a sheet feed shaft which can manufacture, at a low cost, a sheet feed shaft having spike-like projections with high feed or film feed effect by the use of a simple perforating means.
It is another object of this invention to provide a method for manufacturing a sheet feed shaft in which a number of spike-like projections with high feed or film feed effect are formed at a time on the outer periphery of a metallic rod quickly and simply by the perforating processing making use of a press.
For achieving the aforementioned objects, according to the present invention, there is provided a sheet feed shaft in which a plurality of spike-like projections which rise at an obtuse angle, at an acute angle or at right angles in a rotational direction of a metallic rod are formed by plastic processing on the circumferential surface of the metallic rod, said projections being provided in the entire axial direction or in plural areas of the metallic rod.
The apparatus for manufacturing a sheet feed shaft according to the present invention comprises a support bed for supporting a metallic rod, and a punch unit arranged opposite to the support bed to be reciprocated by a press, wherein a pair of perforating members having perforating edges formed on faces opposed to each other are mounted detachably on the punch unit.
Further, a method for manufacturing a sheet feed shaft according to the present invention comprises: supporting a metallic rod on a support bed, and simultaneously applying a perforating processing to two portions in which peripheral surfaces of the metallic rod are opposed by a perforating member formed with perforating edges on faces opposed to each other to form a plurality of spike-like projections whose rising directions are contrary to each other.